A SIMULATION MODEL APPROACH TO ANALYSIS OF HIGH BREAKDOWN VOLTAGE IN NORMALLY-OFF 4H-SiC VERTICAL JUNCTION FIELD EFFECT TRANSISTOR

摘要

In this paper, the temperature dependent breakdo wn voltage characteristics of normall y-o ff 4H-SiC VJFET (Vertical Junction Field Effect Transistor) are simulated using commercially based Sentaurus TCAD simulator. Newly developed impact ionization model is implemented to investigate the breakdown voltage. This physical based model proved to provide compatibility over the wide range of temperatures. The breakdo wn voltage indeed varies with temperature and device exhibits negative temperature coefficient. At gate doping of N gate = 5 x 10 17 cm -3 , the breakdo wn voltage of 14 kV is obtained with leakage current of 2.1 x 10 -7 A. Moreover, the simulation results indicate that with a gate doping of N gate = 1 x 10 18 cm -3 , the breakdown voltage of SiC VJFET is enhanced to 19 kV with leakage current of 3.4 x 10 -8 A. Using finite element simulation, the distribution of electric field and electron velocity as a function of temperature is also analyzed, which is not readily accessible by experimental techniques. The distribution of electric field revealed the punch -through behavior reported first time in our simulation case. In addition, 19 kV SiC VJFET showed 27% higher electric field when compared with 14 kV. The structure layout along with model validation showed that the breakdown voltage of 14 kV has an excellent agreement with experimental reported values.